Enhancement of thermoelectric properties of low-toxic and earth-abundant copper selenide thermoelectric material by microwave annealing

Our current work aims to enhance the thermoelectric properties of p-type copper selenide (Cu2Se), a low toxic, earth-abundant intermediate material for thermoelectric applications by a low-cost, simple and fast microwave-assisted metallurgy route. Hot pressed copper selenide pellets were treated at various temperatures in the range of 250 oC to 425 oC in a microwave furnace. We analyze the variation of several characteristics of the samples, such as electrical, thermal, structural, microscopic, dielectric, and mechanical properties, when the samples are exposed to different annealing conditions. Broadband dielectric spectroscopy (BDS) analysis facilitated the comprehensive study of variation of AC electrical characteristics of the samples such as AC conductivity, dielectric permittivity storage, dielectric loss, and AC capacitance, with temperature and frequency. The results indicate exceptional electrical, thermal, and mechanical properties for samples annealed at 375 oC with high room temperature electrical conductivity of 538.3 S/cm and ultra-low thermal conductivity of 0.59 W/mK. The crystallinity improved as the annealing temperature increased, as did the formation of oxides over 400 oC. The samples have a high strength with maximum nanohardnesss and compression strength of 3.75 GPa and 326.75 MPa, respectively that has been a significant improvement over the existing studies on copper selenides.